This invention relates generally to attachment mechanisms. More particularly, this invention relates to an apparatus for mounting a sensor onto a machine.
In the practice of preventive maintenance of machines such as pumps and motors, it is important to monitor the dynamic and static conditions of the machine. When a machine exhibits anomalous vibrational characteristics, for example, it may be necessary to inspect the machine for repair or maintenance. Many preventative maintenance programs utilize accelerometers to sense vibrational characteristics of the machines. An accelerometer produces an electrical signal which corresponds to the level of vibration produced by the machine acting upon the accelerometer. The accelerometer may be held in contact with a machine test point by a maintenance technician while sensor data is read and stored by a portable data collector/analyzer. Other applications utilize permanent or semipermanent attachment of the accelerometer to the machine by means of mounting hardware. In such applications, the accelerometer output is routed to a computer, thereby providing continuous vibration data to the monitoring system.
One type of accelerometer mount is disclosed in U.S. Pat. No. 4,823,602 to Christensen, Jr., titled, xe2x80x9cAccelerometer Mounting Devicexe2x80x9d. Christensen describes a device for mounting an accelerometer which utilizes multiple component parts, including an external housing component, to mount an accelerometer to a machine. As is typical in the art, this mounting device includes a plethora of mechanical components, increasing the overall cost of the device by requiring a relatively complex manufacturing process for its many components. The device described in the Christensen, Jr. patent also requires a rather complicated procedure of attaching the accelerometer and mounting device to a machine. Furthermore, the mounting hardware described by Christensen, Jr. requires rotation of the sensor for attachment and removal, which further requires that at least one end of the sensor output cable be disconnected to prevent cable twist.
What is needed, therefore, is a simple and effective, low-cost mounting device for mounting a sensor to a machine.
The present invention overcomes the difficulties and disadvantages of the prior art by providing an apparatus for holding a sensor module in sensory contact with a machine to be monitored. The sensor module includes an integral sensor having a central axis, a shoulder, and a substantially planar lower surface. A coupler is provided which includes a lower portion for being attached to a structural element of the machine. With the lower portion of the coupler attached to the machine, an upper portion remains exposed above the machine structure. The exposed upper portion of the coupler includes a substantially planar upper surface which is brought into contact with the substantially planar lower surface of the sensor module with contact between the two planar surfaces maintained by a fastener. In a preferred embodiment, the fastener is a hex nut having an annular lip at one end for engaging the shoulder of the sensor module and having internal threading at the other end for engaging the exposed upper portion of the coupler. When attached to a machine, the fastener and coupler are substantially symmetrically positioned with respect to a central axis of the sensor.